Loader lift linkage



p 1969 T. G. CAMPBELL LOADER LIFT LINKAGE Filed Jan. 8, 1968 INVENTOR TREVOR G. CAMPBELL ATTORNEYS Unite 3,464,574 LOADER LIFT LINKAGE Trevor G. Campbell, Peoria County, Ill., assignor to Caterpillar Tractor Co., Peoria, Ill., a corporation of California Filed Jan. 8, 1968, Ser. No. 696,345 Int. Cl. E02f 3/00 US. Cl. 214-776 3 Claims ABSTRACT OF THE DISCLOSURE In prior art loaders, the lift jacks have commonly been connected directly to the lift arm and acted thereagainst for raising and lowering the bucket. It is often desirable to increase the lift capacity without substantially altering the loader structure or its linkage. Increased lift capacity would contribute to the efficiency of the loader by permitting it to accept greater loads. In addition, increased lift capacity may be desirable or necessary to compensate for increased weight in the bucket assembly such as when an ejector bucket is used. To increase the lift capacity of the prior art loaders, it was necessary, for example, to increase the size of the lift jack or else to increase the moment arm with which they acted against the lift arms. Replacing the lift jacks is undesirable since 7 it increases cost. On the other hand, increasing the moment arm with which the lift jacks act against the lift arms is also undesirable since it decreases maximum elevation for the bucket,

The present invention provides simple means for increasing loader lift capacity by varying the moment arm with which the lift motor means acts upon the lift arm according to varying elevation of the bucket. A greater moment arm is provided for the lift motor means when the bucket is at lower elevations adjacent ground level so that increased lifting capacity is available when most necessary during the loading cycle. As the bucket is raised, the moment arm is decreased to permit maximum elevation of the bucket without increased extension of the motor means.

It is accordingly an object of the present invention to provide a loader with lift linkage having a variable moment arm. Other objects and advantages of the invention will be apparent from the following description With reference to the accompanying drawing.

In the drawing:

FIG. 1 is a side elevational View of the front end of a loader illustrating its lift and tilt linkage with the buckets in a suitable position at ground level for loading; and

FIG. 2 is a fragmentary side elevation view of the loader with its bucket in an elevated position according to the lift linkage.

A loader vehicle is partially illustrated at 11 in FIG. 1 and has a bucket assembly 12 conventionally supported by lift arms, one of which is indicated at 13. Conventional tilt linkage comprises a tilt jack 14 pivotally connected to each lift arm by means of a bellcrank member 16. A lever 17 pivotally interconnects the tilt jack, its lift arm and a link 18 which is also connected to the bucket so that the bucket is tilted according to operation of the jack. The lift arm 13- is pivotally connected to States Patent the vehicle at 19 and the bellcrank member 16 has a central pivotal connection 21 with the lift arm. T o correlate tilt motion with lifting or lowering motion of the bucket assembly, a guide link 22 is pivotally connected at one end 23 to an end of the bellcrank member opposite its connection with the tilt jack. The other end of the guide link 22 is pivotally connected to the vehicle at 25 by means of a tab 24 disposed adjacent the pivotal connection 19 between the vehicle and the lift arm.

A hydraulic lift jack as at 26, is associated with each lift arm and is pivotally connected to the vehicle at 27. According to the present invention, the lift jack is associated with the lift arm 13 through lever means preferably comprising the bellcrank member 16 and the guide link 22 of the tilt linkage. In this preferable structure, the lift jack is connected with the bellcrank member at pivot point 23 along with the guide link.

The advantage of the present lever connection between the lift jacks and lift arms is readily apparent by examination of FIGS. 1 and 2, In conventional lift arrangements where each lift jack is pivotally secured to a lift arm adjacent the pivot pin 21 for example, the moment arm with which the lift jack acts upon the lift arm relative to its pivot point 19 would be decreased somewhat during elevation of the bucket. Thus, in such conventional arrangements, the effective moment arm of the lift jack for any given bucket position is determined only by the relation of the pivotal connections of the lift arm and jack, 19 and 27 respectively, and the conventional pivotal connection of the jack directly to the lift arm.

Variation of the moment arm with which the lift jacks act on the lift arm within the present arrangement is substantially enhanced for increased effectiveness of the lift jack during loader operation. Since each jack is connected to the lift arm at 23 through the bellcrank member 16 and to link 22, the effective pivotal connection 23 between the jack and lift arm describes an are 28 about the pivotal connection 25 of the link during lifting and lowering of the bucket. Accordingly, by the present invention, the effective moment arm for any given bucket position is determined by the relation of the pivotal connections 19 and 27 of the lift arm and jack, the effective pivotal connection 23 between the jack and lift arm and additionally by the pivotal point 25 about which the pivotal connection 23 rotates. Thus, when the bucket is in a loading position, as shown in FIG. 1, the above described arrangement provides an increased effective moment arm for the lift jack. It is in this general position that maximum lift capacity is desired since the bucket may then be employed, for example, in a digging cycle or for breaking off of material loaded into the bucket. On the other hand, as the bucket is raised on its lift arms to the position shown in FIG, 2, the connection between the jack and the lift arm approaches a more favorable location for lift height at an increased rate because of the present lever connection. Thus, the lift jack remains effective for raising the bucket to a suitable height for dumping or ejection of material therefrom while providing an increased break out force at the loading position. It is apparent from the above descripti-on that the increased moment arm, when the bucket is lowered, permits the use of smaller lift cylinders for the same lift capacity or else provides increased lifting capacity without an increase in the size of the lift cylinders. An additional advantage arises from the connection of each lift jack to the pivot connection 23 since a pin connection is eliminated on each side of the loader. Additionally, stresses on the lift arm and the remaining pivot pins .are substantially reduced.

Although the present invention has been described with reference to one particular embodiment, it is apparent that numerous variations are possible within the scope of the invention. For example, the invention is described above with reference to a particular bucket assembly and tilt linkage. However, it is apparent that the invention may also be employed with any bucket-like assembly which is supported on lift arms for both lifting and tilting motion.

I claim:

1. In a bucket loader having a bucket supported by at least one lift arm pivotally connected to its vehicle with extendible motor means for raising the bucket on the lift arm, the improvement comprising:

a lever associated with the lift arm and the motor means for increased variation of the moment arm with which the motor means acts upon the lift arm, relative to the pivotal connection between the lift arm and vehicle according to varying elevation of the bucket on the lift arm, said lever being pivotally interconnected between the lift arm and an extendible end of the motor means, a link being pivotally interconnected between the lever adjacent its pivotal connection with the motor means and a portion of the vehicle which is relatively stationary during raising and lowering of the bucket.

4 2. The bucket loader of claim 1 wherein said lever is formed by a bellcrank member of tilt linkage associated with the bucket and its lift arm.

References Cited UNITED STATES PATENTS 3,392,855 7/1968 Przybylski 214138 HUGO O. SCHULZ, Primary Examiner US. Cl. X.R. 

